It is known to react organic isocyanates with alcohols to prepare urethanes, (Ency. Chem. Tech., 13, p. 789, 1954). It is well-known that isocyanates react readily with primary alcohols at room temperature and with secondary and tertiary alcohols less readily. The normal reaction of an alcohol and an isocyanate is readily catalyzed by mild and strong bases, by many metals, and by acids. The isocyanate reaction can proceed with almost any compound possessing an active or labile hydrogen, i.e., a hydrogen easily replaced by sodium. Beta-hydroxyalkylsulfoxides can possess at least one labile hydrogen.
Beta-hydroxyalkylsulfoxides can be prepared by the method of Anderson, U.S. Pat. No. 3,247,258, which is incorporated by reference, wherein the mercaptan (or thiol), the olefin and oxygen are in contact at temperatures above 80.degree. C. Anderson indicates that with certain olefins and mercaptans such as indene, styrene and thiophenol, the reaction occurs by mixing the olefin and mercaptan first, with the oxygen being bubbled through the mixture thereafter. Other patents such as Oswald, et al., U.S. Pat. No. 3,043,824 and Goodhue, et al., U.S. Pat. No. 3,210,243, which are each incorporated by reference, disclose preparing beta-hydroxyalkylsulfoxides through (1) a co-oxidation route using a hydroperoxide or through (2) oxidation of the sulfide by means of hydrogen peroxide. Oswald indicates that the preparation of hydroperoxide products by olefin-mercaptan co-oxidation to the sulfoxide requires chain initiators, e.g., ultraviolet light and the addition of peroxide compounds (hydroperoxides). In the absence of such catalysts, some co-oxidation reactions have extremely long induction periods and are not practical to carry out. Goodhue teaches that preparation of the sulfoxide using hydrogen peroxide is a three-step synthesis through the sulfide which in turn is prepared from the mercaptan with epichlorohydrin. Fields, in commonly-assigned U.S. Pat. No. 4,040,921, incorporated herein by reference, teaches a one-step process for beta-hydroxyalkylsulfoxides by reacting an olefin and a thiol with oxygen in the presence of a dye sensitizer using visible light at a temperature from -10.degree. to 70.degree. C.
Sulfoxides undergo condensation reactions but typically the condensations do not occur at alpha-methylene groups but proceed to the formation of sulfonium salts, (Ency. Chem. Tech., 13, p. 355, 1954). The low degree of activity of methylenic groups alpha to the sulfinyl group of the sulfoxide indicates that the sulfinyl group does not exert an activating effect comparable to the carbonyl, and the typical reactions of enolization are not observed involving the alpha carbon. However, despite the well-known reaction to prepare urethanes from alcohols and isocyanates, and although it is known that most compounds that contain a hydrogen bonded to oxygen react with isocyanates under proper conditions and that sulfur compounds react in the same manner with isocyanates as their oxygen analogues, but at a much slower rate, the reaction of an isocyanate with a beta-hydroxyethylsulfoxide to produce a carbamate of a sulfoxide compound has not been described previously in the prior art. Carbamates of beta-hydroxyethylsulfoxides accordingly have not been known previously, and their useful properties as cosurfactants have not been evaluated.
The object of this invention accordingly is to produce as new compounds the carbamates of beta-hydroxyethylsulfoxide. These compounds are useful as cosurfactants in enhanced oil recovery, as surfactants and biocides, and as hydraulic fluids when of sufficiently low molecular weight.